Garlic intake and gastric cancer risk: Results from two large prospective US cohort studies

Abstract

Although many case-control studies suggested that garlic intake may reduce gastric cancer risk, evidence from prospective cohort studies has been lacking. We examined the association between garlic intake and subsequent risk of gastric cancer among 77,086 women in the Nurses' Health Study (1984-2014) and 46,398 men in the Health Professionals Follow-Up Study (1986-2014). Relative risks (RRs) and 95% confidence intervals (95% CIs) were estimated using Cox proportional hazards models. We additionally examined garlic intake in relation to Helicobacter pylori (H. pylori) infection among 613 participants using logistic regression. During up to 30 years of follow-up, 292 participants were diagnosed with gastric cancer. The pooled multivariable RR of gastric cancer among participants who ate garlic, as compared to those who did not, were 1.11 (95% CI = 0.81-1.51) for the intake of garlic less than once per week, 0.98 (95% CI = 0.71-1.36) for one to four times per week and 1.39 (95% CI = 0.89-2.17) for five or more times per week (p for trend = 0.23). Similarly, no statistically significant association was observed cross-sectionally between garlic intake and H. pylori infection (comparing five or more times per week to never, pooled multivariable odds ratio = 1.66, 95% CI = 0.89-3.09; p for trend = 0.11). The findings from this large prospective study do not support the hypothesis that high garlic intake reduces risk of gastric cancer.

The association of garlic with Helicobacter pylori infection and gastric cancer risk: A systematic review and meta‐analysis

“…Table displays the characteristics of the included studies. A total of 18 studies with 142 921 subjects (5123 cases) published from 1989 through 2018 were identified, of which 15 were case‐control studies (4573 cases), 1 was case‐cohort study (152 cases), 1 was cohort study (292 cases), and 1 was randomized controlled study (106 cases) . Six of these studies were conducted in China, 2 in Sweden, 2 in Iran, 1 in Italy, 1 in South Korea, 1 in Lithuania, 1 in Netherlands, 1 in Turkey, 1 in Uruguay, 1 in the United States, and 1 in Venezuela.…”

“…Up to now, a total of 13 studies with 4889 participants investigated the association between garlic intake and H. pylori (Table ), 10 of which did not found a significant result. Six studies were conducted in Asia (3 in China, 2 in Iran, and 1 in Japan), 6 were in Europe (3 in Turkey, 1 in Bulgaria, 1 in Germany, and 1 in the United Kingdom), and 1 was in the United States.…”

“…Twenty‐one studies met the above criteria, whereas one study was excluded for not being able to calculate 95% CI, one for garlic used as part of the intervention and not being separated from the regimen, and one for garlic not being separated from other allium vegetables (Figure ) . A total of eighteen studies were included in the final analysis …”

“…Recently, Kim et al used the prospective data of 123 484 participants from the Nurses’ Health Study and the Health Professionals Follow‐up Study and did not find supportive evidence for the hypothesis that garlic reduced the risk of gastric cancer . The other cohort study and two randomized controlled trials by far likewise found no significant effect of garlic on gastric cancer prevention.…”

“…Garlic can therefore be a potential pharmaceutical candidate for treating and preventing H. pylori infection, and H. pylori induced gastric diseases such as gastric cancer. However, evidence from epidemiological studies does not consistently support the antibacterial effect of garlic on H. pylori . One randomized controlled study using 7.3 years of garlic extract and oil as the intervention found no eradication effect on H. pylori infection, while another randomized trial yielded a significant 24% increase in eradication rate after adding allicin to standard eradication regimen .…”